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'Cyclic Voltammetry' in keywords Facet   Publication Year 1993  [X]
Facet   section ZfN Section B:Volume 048  [X]
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1Author    Alexander Lichtblau, Hans-Dieter Hausen, Wolfgang KaimRequires cookie*
 Title    First Structural Characterization of an Easily Oxidized Derivative o f 1,4-Dihydroquinoxaline  
 Abstract    The first crystal structure analysis o f a 1,4-dihydroquinoxaline is described by example o f the l,4-bis(re/-/-butyldimethylsilyl) derivative. In the solid state, this molecule exhibits a non-planar heterocycle with a dihedral angle o f 156.3° along the N -N axis in the boat-shaped 87r electron ring system. The alkyl groups o f the Si(/er/-Bu)M e2 substituents are arranged as to minimize steric repulsion. Despite the reduced n electron conjugation due to non-planarity, the com pound is oxidized reversibly to an EPR detectable radical cation at -0 .5 9 V vs. ferro­ cene in dichloromethane. However, the second oxidation to the fully aromatic dication is elec-trochemically irreversible. A comparison with previously obtained results illustrates the struc­ tural flexibility o f the non-aromatic 1,4-dihydro-1,4-diazine ring system which is strongly affected by rather weak non-bonded interactions. 
  Reference    Z. Naturforsch. 48b, 713 (1993); eingegangen am 21. Dezember 1992 
  Published    1993 
  Keywords    Heterocycles, Organosilicon Compounds, Crystal Structure, Cyclic Voltammetry, Conformation 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-0713.pdf 
 Identifier    ZNB-1993-48b-0713 
 Volume    48 
2Author    Michel Mégnamisi-Bélombé, Irene Jokwi, Emmanuel Ngameni, R. Obert Roux, Bernhard NuberRequires cookie*
 Title    X-Ray Structure, Electrochemical and Electronic Spectroscopic Examination of Cobaloximatic Acid: Hydro-fraw5-diiodobis(ethanedioximato(l-)-N,N')cobaltate(III). Extended Intermolecular O-H-O Bridging in the Solid  
 Abstract    The structure of the cobaloximatic acid, hydro-rrans-diiodobis(ethanedioximato(l-)-N,N')cobaltate(III), has been determined by X-ray diffraction. Crystal data: C4H7CoI2N40 4, Mr = 487.87; monoclinic space group P2xta (C|h); a -10.795(7), b = 9.003(7), c = 11.881(6) Ä; ß = 97.29(6)°; V = 1145.35 Ä3; Z = 4; dc = 2.83 Mg n r3. Rw (R) = 3.6 (3.9)% for 3064 observed independent reflections and 148 parameters. The coordination geometry around Com is a dis­ torted (4 + 2) octahedron of four chelating equatorial N atoms and two apical iodides. The compound is most adequately formulated as a monovalent strong acid: H(Co(GH)2I2) (GH_ = ethanedioximate or glyoximate). The H atoms of the oxime groups are involved in the usual mframolecular, as well as in much stronger internlolecular O -H -O bridgings (O — Ointramol = 2.613-2.631, O — Ointervo, = 2.454 Ä). The "acidic" H atom of each molecule participates in the intennolecular bridging which extends throughout the structure, and propagates nearly parallel to the [101] crystallographic direction. The redox properties of the present compound were examined by cyclic voltammetry in acetonitrile solution at room tem­ perature. Redox waves attributed to the reduction of Co11 1 and to the oxidation of T were ob­ served, along with a wave which may be linked to the reduction of the "acidic" proton. 
  Reference    Z. Naturforsch. 48b, 1360—1364 (1993); received May 17 1993 
  Published    1993 
  Keywords    X-Ray, Cobaloximatic Acid, Extended Hydrogen Bridging, Cyclic Voltammetry 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-1360.pdf 
 Identifier    ZNB-1993-48b-1360 
 Volume    48